This study involves the design of an online course on oral corrective feedback (ONOCEF) and its implementation through flipped classroom with a view to finding out if it exerts any impact on ELT student teachers' competencies regarding oral corrective feedback (OCF). Having conducted a needs analysis, the ONOCEF was developed and then administered to thirty ELT student teachers by flipping the classroom. In this flipped model, first, the students took the ONOCEF input outside the school. Then they enacted this input in their microteachings alternately in formal classes. Following each performance, reflection papers were gathered from the non-performing student teachers (NPSTs) in order to evaluate their performing peers' (PSTs) OCF practices and thus reveal the ONOCEF components in their microteachings. Content analysis of the reflection papers demonstrated positive effects of the ONOCEF on both the PSTs' and NPSTs' competences concerning OCF. Through the ONOCEF, the PSTs were able to provide OCF effectively and use different OCF strategies while the NPSTs were successful locating their performing peers' non/corrections and identifying the shortcomings in their OCF practices. As a result, the ONOCEF proved to be an effective online tool to help pre-service ELT teachers promote their competences regarding OCF.